Dieselgate - VW Group Emission ScandalDiscussion around the VW Dieselgate Emissions scandal. Details and news updates can be viewed here: http://forums.tdiclub.com/showthread.php?goto=newpost&t=448336
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The only way this will be scientific is to pre fix test and then post fix same car on a dyno. Second best: someone who keeps hand calculated records, look up what they got under similar driving conditions for 5 tanks last winter vs 5 tanks now.

When I went in to get emissions tested I choose a facility that offered dyno print out for a little extra money.. unfortunately their printer was broken and they wouldent sell it to me.

Ive got every fuel receipt since I owned it, for the last 10k miles.. but it would be nice to get graphs of the original tune, the fixed tune, then my fixed-fix stage 2 tune.. but thats not gonna be cheap to get :\

Might record some 0-60 runs in Drive and Sport just too compare what they did to the shift points.. I can do that for free.

My 2013 Q7 feels like a lesser car now for sure. You can’t feather the gas and have any effect, merging into traffic feels way more dangerous because the timing is way worse. I have to basically drive it in sport mode when merging or changing lanes or risk an accident. Feels like it will refuse to downshift unless you press down hard, and then when it does it drops you multiple gears.

Just got my 2014 Touareg TDi fixed at dealer. Driven 2 weeks now post modification. Contrary to VW claim, I can say with certainty that 1) the car lost a lot more than 1 MPG. I am seeing mpg value as low as 18.5 which never happened in my pre -mod 27,000 miles of driving under any condition. I was getting 31-32 on highways pre-mod. Will find out later how much MPG loss in highway condition. 2) there is significant loss of accelerations power. This was one of the character I like the most. 3) the engine sound noisier all the time with a completely different feel when driving. My conclusion, I am getting a much worse different car after VW modifying it. I believe VW deliberately understated the changes resulted from the emission modification.

I was not angry when VW was first caught cheating. I am much angrier now realizing that they decided to cheat their consumers out the second time and our government appears to be helping them rather than us.

1) the car lost a lot more than 1 MPG. I am seeing mpg value as low as 18.5 which never happened in my pre -mod 27,000 miles of driving under any condition. I was getting 31-32 on highways pre-mod. Will find out later how much MPG loss in highway condition.

Until you document miles driven against fuel you actually pump into the tank you can't claim a mileage hit post-fix. The car's calculation of mileage is notoriously inaccurate, and may be more-so with VW having been mandated to change operational parameters of the engine, but not being required to make the MFI accurate.

Also, mileage MAY increase as the vehicle learns and adjusts certain values.

I'm not saying people's mileage didn't drop.. I'm saying going by the MFI is not an accurate way to support that argument.

Until you document miles driven against fuel you actually pump into the tank you can't claim a mileage hit post-fix. The car's calculation of mileage is notoriously inaccurate, and may be more-so with VW having been mandated to change operational parameters of the engine, but not being required to make the MFI accurate.

Also, mileage MAY increase as the vehicle learns and adjusts certain values.

I'm not saying people's mileage didn't drop.. I'm saying going by the MFI is not an accurate way to support that argument.

Truly not trying to be antagonistic here. I get that calculating MPG by taking odometer reading and dividing by fuel burned is a more accurate determinant of MPG. I also get that comparing pre-"fix" calculations by hand with post-fix MFI readings tells little about relative MPG pre- vs. post-"fix." But what I don't get is why comparing pre-"fix" MFI readings with post-"fix" MFI readings isn't a valid indicator of whether the "fix" has adversely affected MPG.

So long as it's an apples-to-apples comparison, why isn't comparing pre- vs post-"fix" MFI readings a reliable way to see if your TDI is less fuel-efficient post-"fix"? For example - if I got 28 MPG on my MFI pre-"fix" and now get 24 MPG on my MFI post-"fix", why can't I draw the conclusion that the "fix" hurt fuel efficiency? My MFI MPG was consistent pre-"fix" at about 1 MPG over hand calculation, and since it was consistently the same 1 MPG off, time after time, I don't consider it "notoriously inaccurate."

Again, not trolling for a fight. I just don't understand why comparing apples-to-apples is invalid.

Truly not trying to be antagonistic here. I get that calculating MPG by taking odometer reading and dividing by fuel burned is a more accurate determinant of MPG. I also get that comparing pre-"fix" calculations by hand with post-fix MFI readings tells little about relative MPG pre- vs. post-"fix." But what I don't get is why comparing pre-"fix" MFI readings with post-"fix" MFI readings isn't a valid indicator of whether the "fix" has adversely affected MPG.

So long as it's an apples-to-apples comparison, why isn't comparing pre- vs post-"fix" MFI readings a reliable way to see if your TDI is less fuel-efficient post-"fix"? For example - if I got 28 MPG on my MFI pre-"fix" and now get 24 MPG on my MFI post-"fix", why can't I draw the conclusion that the "fix" hurt fuel efficiency? My MFI MPG was consistent pre-"fix" at about 1 MPG over hand calculation, and since it was consistently the same 1 MPG off, time after time, I don't consider it "notoriously inaccurate."

Again, not trolling for a fight. I just don't understand why comparing apples-to-apples is invalid.

First, because of small sample size. How many tanks did it take to arrive at an MFI pre fix? How many tanks post fix?

With the small sample, you have all sorts of variables: diesel blend and quality, route, traffic, headwind, who knows? My Touareg showed up to a 15% variation in MPG from one tank to another on I-75 trips back in the day. One time I had a 31.5 mpg tank but typically it was 26-28. I would stop at the same pumps but in different season and in different weather. The 31.5 tank was when there was a stiff south westerly wind literally blowing me all the way from Virginia to New Hampshire. I hand calculated everything and was totally perfectionist about filling the tank exactly the same amount every time, zeroing out and record keeping. If hand calculating showed this much spread, the MFI will show even a bit more.

So long as it's an apples-to-apples comparison, why isn't comparing pre- vs post-"fix" MFI readings a reliable way to see if your TDI is less fuel-efficient post-"fix"? For example - if I got 28 MPG on my MFI pre-"fix" and now get 24 MPG on my MFI post-"fix", why can't I draw the conclusion that the "fix" hurt fuel efficiency? My MFI MPG was consistent pre-"fix" at about 1 MPG over hand calculation, and since it was consistently the same 1 MPG off, time after time, I don't consider it "notoriously inaccurate."

Again, not trolling for a fight. I just don't understand why comparing apples-to-apples is invalid.

Because its well known that getting an aftermarket tune borks the MFI and it needs re-calibrated afterwords.. When my 2.0L got tuned the MFI went from being pretty accurate compared to hand calculations to far off from hand calculations..

If MFI thinks that injectors firing so many times == so much fuel, and then they tweak how long injectors are open or the pressure of the fuel then suddenly the MFI's calculations are nonsense until manually adjusted to compensate.. it could think its using more fuel than it actually is pretty easily with the fix in place..

also calculating it by the tank averages it out better, the long average on MFI isint that far out.. for example, if you just had a regen its usually not that accurate either.

Truly not trying to be antagonistic here. I get that calculating MPG by taking odometer reading and dividing by fuel burned is a more accurate determinant of MPG.

.....

Again, not trolling for a fight. I just don't understand why comparing apples-to-apples is invalid.

Others brought up good points but I had one big point to add.

We don't know exactly how fuel economy is calculated, and whether anything about those calculations changed with the fix.

Yes, I get that you can calculate fuel use over distance, but there is no direct measurement of injected fuel volume. There are calculations based on measured fuel pressure, injector open duration, and an offset entered into the ECU to tell it exactly how much each injector flows (the fact that this changes over time isn't relevant to this conversation, but is to overall reported MFI on a high-mileage vehicle).

Even then, does it compare calculated fuel use per hour, then adjust that by MPH to get MPG? Does it calculate fuel usage over a 100yd distance? 1/4mile?

Ultimately there is a lot we don't know about the inner workings of the ECU, as well as what exactly the fix did. We don't know whether some element of the fix could have impacted the way the ECU does FE calculations for the MFI.

Basically, there are too many unknown variables. Until you compare actual fuel pumped vs actual odometer change it isn't a valid comparison. Even the difference in how one fuel pump shuts off vs another or the tendency of the fuel to foam or not can impact this measurement, but as long as the fuel pumps are calibrated this will average out pretty quickly over a few tanks.

That said, I'm on my first tank post-fix and with 1/4 left it sure seems like I'll get significantly less miles out of it. But, I'll calculate MPG for this tank and a couple more (to allow for adaptation within the ECU to the way I drive) before drawing a conclusion.

My gut is telling me that I lost significant FE. I'll wait to complain about it until I have hard numbers.

Does anyone else notice their engine warms up much faster than before? I don't have a complaint about this, but I do worry about how they are doing it. One can only assume that they are doing significantly more EGR than before to get everything up to temp. Not a big deal, but too much EGR is hard on an engine and is also bad for engine oil quality. If I plan to keep this Touareg a while, I'm wondering if this is going to be detrimental to the longevity of the engine. Granted it's all under warranty now, but not in a few years when I'm over 120k and VW is no longer taking care of the bill.